Equipment

Recently, my attention has been captured by some Direct Digital integrated amplifier-DACs: NAD’s Masters Series M2 and C 390DD. My own budget reference, the NuForce DDA-100, is of similar design. Each of these models sounds fantastic for its price, and I like the idea of keeping the signal entirely in the digital domain, right up until the speaker outputs.

When NAD announced the newest power amplifiers in their top line, the Masters Series, I was surprised to learn that they would be class-D amps with conventional analog inputs, not Direct Digital designs. Also offered are the matching Masters Series M12 stereo digital preamplifier-DAC and M17 surround processor, but these link to the new Masters Series power amps only via analog RCA or XLR connections.

I received for review a Masters Series M27 seven-channel power amplifier ($3999 USD). A review of the M17 surround-sound processor will follow on April 15.

Description

NAD uses many different circuit topologies in their amplifiers, including the more traditional class-A/B in most of their designs, and class-D in the Direct Digital amplifier-DACs, which are based on Direct Digital Feedback Amplifier technology. Their budget D 3020 integrated amplifier-DAC, a reimagining of their classic 3020 integrated, is also a class-D design, but uses Hypex’s UcD technology and a conventional built-in DAC section. The Masters Series M27 power amplifier, and the stereo M22, uses Hypex’s latest, most advanced Ncore, class-D amplification modules. For more about Hypex, their technologies, and their chief engineer, Bruno Putzeys, see Pete Roth’s article “Searching for the Extreme,” at SoundStage! Ultra.

According to Greg Stidsen, director of technology and product planning for Lenbrook International, the parent company of NAD, PSB, and Bluesound, the M27 uses Ncore circuitry in its custom-designed output stage. They then control the power supply to provide the same continuous power output into 4 or 8 ohms, which allows higher peak current capability, which is said to be more meaningful for real-world performance than continuous power output. The amplifier protection function has also been moved from the output stage to the power stage in the switch-mode power supply, to shorten the signal path and improve speed and safety, as well as some other aspects of the implementation of the Ncore technology that are unique to NAD.

In my correspondence with Stidsen, it became apparent that NAD was not abandoning Direct Digital integrated-DACs in favor of Hypex-based hybrid digital power amplifiers. Instead, these new Hypex Ncore-based power amps are another way for NAD to provide what they believe to be class-leading performance at particular price points.

DIYers have been making their own Hypex Ncore amplifiers for several years now, but the only other commercially available Ncore amps I can think of are two monoblock models: the Mola-Mola Kaluga ($18,000/pair), designed by Bruno Putzeys, and Bel Canto Design’s MPS1 ($30,000/pair). I’ve heard the MPS1 as part of Bel Canto’s all-digital Black system, and it sounded spectacular in the short time I was able to listen to it under the less-than-ideal conditions of a suite in the Venetian hotel during the 2014 Consumer Electronics Show. At $3999, the M27 is far less expensive, and can provide amplification for a seven-channel home-theater system. NAD claims that, driving all seven channels, the M27 can produce 180Wpc continuous power and over 300W of peak power.

The M27 measures a manageable 17.1”W x 6.2”H x 15”D and weighs 31.1 pounds. The looks of the new Masters Series models are an incremental improvement over the already attractive earlier models in this line. The case is mostly made of very thick, high-quality brushed aluminum, with black panels on the front and top. There are 12 large square grilles on top for ventilation. The feet are metal spikes; magnetic discs are provided to place under the feet to protect whatever surface the M27 is placed on.

A small capacitive touch button on the top edge of the front panel toggles the M27 between Standby and On. The light surrounding the NAD logo glows red in Standby mode, faintly blue when On, and can be dimmed with a switch on the rear.

Neatly spaced across nearly the full width of the rear panel are sets of RCA and XLR input jacks, with switches to select between them, as well as high-quality speaker binding posts. There are also the main power rocker switch, a 12V DC trigger, and an IEC inlet for the removable power cord.

Overall, the M27 has an attractive, modern look, with build quality to match.

Setup

The NAD Masters Series M27 took the place of: my reference Anthem Statement M1 monoblock amplifiers, which I use for my surround system’s front left and right channels; a Bel Canto eVo6 that I run in bridged mono mode to power the center and surround channels; and a Parasound Halo A 31 three-channel amp (in for review). The speakers were my usual KEF R900 mains, R600C center, Definitive Technology BP-8080ST surrounds, and two Paradigm Reference Servo-15 v.2 subwoofers. For two-channel listening, I used a pair of Definitive Technology Mythos ST-Ls.

When I first received the M27, I listened to it briefly to confirm that it was working properly. Then I unplugged it from my system to concentrate on completing a review of the Parasound Halo A 31. During that time, I used the M27 to occasionally drive my surround speakers, to give it some hours of break-in before doing any serious listening.

Masters class

Some readers will probably wonder if, after listening to Parasound’s outstanding Halo A 31 class-A/B amplifier ($3300) for a long while, I found NAD’s class-D Masters Series M27 as engaging.

Yes. The sound of the M27, especially through its balanced inputs from either the Anthem Statement D2 A/V processor or the dedicated stereo outputs of the Oppo BDP-105 universal Blu-ray player, was simply dazzling. Its sound wasn’t quite as rich or full-bodied as the Halo A 31’s, but it still sounded very smooth, and was more transparent, presenting larger, deeper soundstages and more precise imaging.

I was continually amazed at how effortlessly the M27 could articulate individual notes made by instruments and voices on a soundstage as deep as anything I’ve experienced in my system. The imaging in “Somewhere Down the Crazy River,” from Robbie Robertson’s Robbie Robertson/Storyville: Expanded Edition (16-bit/44.1kHz FLAC, Universal), was spooky and holographic. Percussion danced around the soundstage, while Robertson’s raspy voice was anchored rock-solid between the front speakers. “Broken Arrow” had an even bigger soundstage, with exceptional layering of sound from front to back, and the bass in “Fallen Angel” was plentiful but controlled. With every track, the soundstage was not only deep but extremely wide and precisely defined.

The arrangements Jackson Browne uses in his Solo Acoustic Vol.2 (16/44.1 FLAC, Inside) consist of only a guitar or piano, and highlight the introspective lyrics of the mostly lesser-known songs that comprise this highly recommended album. Through the M27, Browne’s voice in “Somebody’s Baby” had incredible presence. This was not accomplished by artificially pushing the sound forward. Everything was at the perfect depth, but there was an incredible purity to the midrange, and precise imaging that gave Browne’s voice a pristine, expressive quality. Even when his voice cracked ever so slightly, the M27 reproduced this with a purity and agility that conveyed the emotiveness of Browne’s performance.

The M27’s transparent sound was nearly devoid of grain. This gave the voices on Foreigner’s Acoustique (16/44.1 FLAC, AIS) a totally crystalline quality, and let me hear every nuance of this “unplugged” album like never before. The guitars and percussion in “Cold as Ice” were placed so precisely on the soundstage, with a totally dark background and a naturalness in the soaring voices, that I was left amazed at the lack of coloration and the dimensionality of the soundstage. And when I required the M27 to crank out party tunes, it did so without complaint. I played one of Doug Schneider’s favorites, “You Shook Me All Night Long,” from AC/DC’s Back in Black (16/44.1 FLAC, Atlantic), as well as my own favorite from that album, the title track -- the sound was still as clean and clear as it had been at lower levels with higher-quality recordings. But this was at levels that raised my wife’s ire -- I soon had to ramp down the volume and put away the air guitar.

The M27’s clarity and huge sense of space with The Expendables 3 on Blu-ray was first-rate, and provided a superb home-theater experience. Every sound effect and word of dialogue was clearly audible among all the bass-heavy action. Even with the multitude of explosions and gunfire, the sound remained open and clear. The compact M27 had plenty of power to drive my KEF R900 mains and R600C center speaker up front and, around back, the Definitive Technology BP-8080STs. Admittedly, the DefTechs have built-in powered subwoofers, so they aren’t as power hungry as most passive speakers. Although rated a somewhat modest 180Wpc, the M27 was typical of NAD products in sounding more powerful than its claimed spec. It wasn’t quite the beast the Halo A 31 is, but held its own against the much larger, 250Wpc Parasound. Pushed hard, the M27 didn’t sound quite as smooth and composed as the Halo with another action movie, Edge of Tomorrow -- there was also a little less weight to the sound -- nor did gunfire have the same impact; with the NAD, I couldn’t as easily feel the concussions of weapons. The NAD’s soundstage was bigger, though, with more precise placements of effects -- the surround soundscape was thoroughly enveloping. Considering that the A 31 has only three channels and the M27, costing just $700 more, has seven, and can be used to power an entire home-theater system, the NAD is a tremendous bargain.

With high-resolution multichannel music recordings, the M27’s pristine sound provided a balanced, 360-degree soundstage of amazing fidelity. The 5.1-channel MLP tracks from the Talking Heads’ Speaking in Tongues (CD/DVD DualDisc, Warner) had great clarity in all channels, especially the extremely active surrounds, which imaged eerily at the sides and back of the room. I heard the same effect with the Blue Man Group’s Complex (DVD-Audio, Lava/DTS). In “Sing Along,” the voice of Dave Matthews emanated lucidly from the center channel, but also very clearly from every other speaker as he provided his own backing vocals in complexly layered harmony. A variety of percussive instruments and the Blue Man Group’s trademark PVC-pipe “drums” delightfully imaged throughout my room with every track.

In many ways, the sound of the NAD M27 reminded me of my reference Anthem Statement M1s, which are 1000W monoblocks ($7000/pair). What I noticed most about both models was what I didn’t hear -- both are extremely neutral, with exceptionally low noise floors. Each floated an exceptionally clean image of Lorde’s voice on her Pure Heroine (24/48 FLAC, Lava/Republic), with an unforced quality at just the right depth in the soundstage. Although it sounded more powerful than its 180Wpc spec, the M27 didn’t have the seemingly endless power reserves of the much more expensive Anthems. Considering the disparities in price and power rating, the NAD still had good control of the bass, keeping a tight grip on the woofers of the KEF R900s. In comparison, the Parasound Halo A 31 had a fuller bottom end, but was slightly less controlled with the R900 speakers.

Head of the class

Although in this review I’ve compared the NAD Masters Series M27 directly with Parasound’s Halo A 31, I’m sure some readers will still be wondering what I really think of the sound of the class-D NAD vs. that of the class-A/B Parasound. Overall, I slightly preferred the Parasound. To be sure, the Halo A 31 has a sound of its own -- it’s not as neutral as the M27. But, as Doug Schneider said in his review of Sonus Faber’s Olympica III speaker, even though it “had a slight sonic signature, it still sounded ‘right’ to me.” That’s how I feel about the Parasound Halo A 31.

But when you think that it would cost a total of $7290 to purchase the Parasound five-channel Halo A 51 ($4795) along with the two-channel Halo A 21 ($2495) in order to equal the seven channels of the M27, the value of the M27 ($3999) becomes apparent. The M27 also packs all seven channels of its efficient amplification into a single compact case -- no insignificant consideration in a real-world system.

In the Masters Series M27, NAD has succeeded in delivering a practical, cost-effective implementation of Hypex’s excellent-sounding Ncore amplifier technology. If you’re looking for a powerful, extremely high-quality, seven-channel amplifier that won’t break the bank, I can’t recommend the M27 highly enough. In fact, I can’t think of a comparable product in this price range.